The present invention relates to an image forming apparatus used for, for example, an electrostatic type recording apparatus or electrophotographic device, an image forming method and a developing agent applied to these apparatus and method.
Conventionally, there is a technique, as disclosed in, for example, Jpn. Pat. Appln. No. 2001-51443, designed to reduce abrasion of the photosensitive layer of a photoreceptor drum by externally adding or mixing metal soap to a developing agent. In this technique, the metal soap is supplied together with the developing agent to the surface of the photoreceptor, and therefore it is considered that the abrasion of the photoreceptor by the cleaning blade can be reduced due to the slipping effect of the metal soap. As the lifetime of the photoreceptor drum is prolonged, it becomes possible to provide print images at a low cost. However, with the addition of a metal soap, the fluidity of the developing agent is lowered. As a result, a deterioration of image, which is called rough surface, occurs. In particular, full-color images of the skin colors of persons, blue sky or the like are significantly deteriorated. In order to avoid this, it is conventionally necessary to limit the amount of addition of the metal soap.
The object of the present invention is to reduce the abrasion of the photosensitive layer and provide a high image-quality full-color image at a low cost.
According to the first aspect of the present invention, there is provided an image forming apparatus comprising:
an image carrier;
a plurality of developing devices located to face the image carrier and configured to form a developing agent image by developing a static latent image formed on the image carrier;
a transfer device configured to transfer the developing agent image onto a transfer material;
a cleaning device provided in a downstream of the transfer device and configured to collect a remaining developing agent on the image carrier; and
a fixing device having a heating member and configured to fix the developing agent image transferred on the transfer member,
wherein one of the plurality of developing devices contains a yellow-color developing agent containing a yellow coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap and another one of the plurality of developing devices contains a black-color developing agent containing a black coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap.
Further, according to the second aspect of the present invention, there is provided an image forming method comprising:
forming a static latent image on an image carrier;
forming a developing agent image by using a developing agent selectively supplied from a plurality of developing devices including a yellow-color developing device containing a yellow-color developing agent containing a yellow coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap and a black-color developing device containing a black-color developing agent containing a black coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap;
transferring the developing agent image onto a transfer material;
cleaning a developing agent remaining on the image carrier after the transferring with use of a cleaning unit; and
fixing the transferred developing agent image onto the transfer member.
Furthermore, according to the third aspect of the present invention, there is provided a combination of developing agents applied to an image forming method apparatus including a plurality of developing devices configured to form a developing agent image by developing a static latent image, comprising: a yellow-color developing agent to be contained in one of the plurality of developing devices, containing a yellow coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap and a black-color developing agent to be contained in another one of the plurality of developing devices, containing a black coloring agent, a binder resin and 0.01 to 5% by weight of a metal soap.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be leaned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.